In related art, a seat for an automobile has been known which has a so-called tilt down mechanism configured to sink down a seat cushion in conjunction with forward tilting down movement of a seat back, thereby lowering the entire seat (see JP-A-2009-154682). The tilt down mechanism is configured to suspend a rear part of the seat cushion to the seat back by a link and to obliquely push down the entire seat cushion in a front-lower direction as the seat back is tilted down forward.
According to the above technology, the rear part of the seat cushion is suspended to the seat back by the link. For this reason, since a position of the seat cushion is changed even when a backrest angle of the seat back is tilted rearward, a ride quality is deteriorated. It is therefore an object of the present invention to prevent a seat cushion from moving upon adjustment of a backrest angle of a seat back even when a seat is provided with a tilt down mechanism.